The aim of this proposal is to develop DNA chips capable of detecting and characterizing mutations in the human CYP2D6 (cytochrome P450 2D6) gene. These chips will be used to correlate drug metabolism phenotype with specific mutations that occur naturally in the human population. CYP2D6 mutations result in dramatic differences in drug efficacy and toxicity for 5-10% of the Caucasian population and 2% of Asian populations. In Phase I, the plan is to: (1) design and synthesize DNA chips complementary to exons 1-9 and intron/exon splice sites of the CYP2D6 gene (1567 coding bp and 180 intron bp); (2) develop a PCR amplification strategy using multiplex PCR for the genomic form of the gene; and (3) develop a hybridization protocol that will test the sequence calling performance of the DNA chips. During Phase II, clones with known CYP2D6 mutations will be used as model targets to test heterozygous and homozygous mutant detection. Finally, they will test the DNA chips for their mutation detection performance in characterized and uncharacterized genomic DNA samples obtained from phenotyped patients.